From 7e38017557bc0b87434d184f8804cadb102bb903 Mon Sep 17 00:00:00 2001 From: Andreas Petlund Date: Thu, 18 Feb 2010 04:48:19 +0000 Subject: net: TCP thin dupack This patch enables fast retransmissions after one dupACK for TCP if the stream is identified as thin. This will reduce latencies for thin streams that are not able to trigger fast retransmissions due to high packet interarrival time. This mechanism is only active if enabled by iocontrol or syscontrol and the stream is identified as thin. Signed-off-by: Andreas Petlund Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'net/ipv4/tcp_input.c') diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 3fddc69ccccc..788851ca8c5d 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -89,6 +89,8 @@ int sysctl_tcp_frto __read_mostly = 2; int sysctl_tcp_frto_response __read_mostly; int sysctl_tcp_nometrics_save __read_mostly; +int sysctl_tcp_thin_dupack __read_mostly; + int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; int sysctl_tcp_abc __read_mostly; @@ -2447,6 +2449,16 @@ static int tcp_time_to_recover(struct sock *sk) return 1; } + /* If a thin stream is detected, retransmit after first + * received dupack. Employ only if SACK is supported in order + * to avoid possible corner-case series of spurious retransmissions + * Use only if there are no unsent data. + */ + if ((tp->thin_dupack || sysctl_tcp_thin_dupack) && + tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 && + tcp_is_sack(tp) && !tcp_send_head(sk)) + return 1; + return 0; } -- cgit v1.2.3 From 6830c25b7d08fbbd922959425193791bc42079f2 Mon Sep 17 00:00:00 2001 From: Lennart Schulte Date: Wed, 17 Mar 2010 02:16:29 +0000 Subject: tcp: Fix tcp_mark_head_lost() with packets == 0 A packet is marked as lost in case packets == 0, although nothing should be done. This results in a too early retransmitted packet during recovery in some cases. This small patch fixes this issue by returning immediately. Signed-off-by: Lennart Schulte Signed-off-by: Arnd Hannemann Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'net/ipv4/tcp_input.c') diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 788851ca8c5d..c096a4218b8f 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2511,6 +2511,9 @@ static void tcp_mark_head_lost(struct sock *sk, int packets) int err; unsigned int mss; + if (packets == 0) + return; + WARN_ON(packets > tp->packets_out); if (tp->lost_skb_hint) { skb = tp->lost_skb_hint; -- cgit v1.2.3